Meiobenthic Organisms as Indicators of Mixing Processes in the Baltic Surface Sediments*     

Janusz Pempkowiak  Joanna Kozuch  Maria Szymelfenig 《Marine Ecology》1996,17(1-3):175-179

Abstract. Two sediment cores were collected in the southern Baltic Sea and sliced into 1.0cm-thick layers. Sediments of each layer were analysed for activities of ²¹⁰Pb, ¹³⁷Cs, ¹³⁴Cs and for the density of meiobenthic organisms (meiofauna). Zones with the rapid mixing occur in the uppermost layers (0–3 cm) of the cores based on ^I34Cs profiles. The extent and density of meiofauna confirmed the rapid mixing and revealed layers with slow mixing (4–8 cm). Sedimentation rates were derived from ²¹⁰Pb profiles below the mixing zones (1.21 and 1.72 mm a-^I) and were confumed by ¹³⁷Cs distribution. Of twenty-one major meiofauna taxa commonly found in the Baltic sediments, three were present in the cores.  相似文献   

河南省卢氏县张家山铁矿地质特征及成因浅析     

周红春  刘传权  郭克剑  彭松民  张毅星  王凌云 《华南地质与矿产》2008,(2):43-48

通过对张家山铁矿床矿体与围岩的接触关系、蚀变特征、矿石的矿物组合、化学组分等地质特征及成因的分析研究,认为张家山铁矿床应属风化淋滤型铁矿床,其原生矿床为铁多金属硫化物矿床,并厘定了该地区铁矿的找矿标志。  相似文献   

Mesozoic-Cenozoic tectonics and geodynamics of Altai, Tien Shan, and Northern Kazakhstan, from apatite fission-track data     

M.M. Buslov  D.A. Kokh  J. De Grave 《Russian Geology and Geophysics》2008,49(9):648-654

Apatite fission-track (AFT) thermochronological modeling as a diagnostic tool for periods of stability (peneplanation) and tectonic activity (orogeny) has been broadly used in tectonic studies of Central Asia in recent years. We discuss more than 100 AFT ages of samples from the Kyrgyz Tien Shan and Altai and compare them with AFT data from northern Kazakhstan. Geological, geomorphological, and AFT data indicate intense activity in the Late Cenozoic Eurasian continental interior. The impact from the India-Eurasia collision on the northern Tien Shan, Altai, and northern Kazakhstan regions showed up at 11, 5, and 3 Ma, respectively, as a result of stress propagation into the continent, with the ensuing reactivation and mountain growth. We hypothesize that a distant effect of the Late Cenozoic India-Eurasia collision was to rejuvenate Paleozoic fault zones and to deform the Mesozoic sedimentary cover north of the collision front as far as the West Siberian Plate. The reactivation facilitated formation of tectonic oil and gas traps. The activity in northern Central Asia under the effect of the Indian indentation into Eurasia appears to continue and may evolve to include uplift of southern West Siberian plate with uplift.  相似文献   

震前卫星热红外环形应力场特征   总被引：6，自引：1，他引：5  

强祖基  姚清林  魏乐军  赵勇  郭坚峰  曾佐勋  谢红接 《地球学报》2008,29(4):486-494

本文包括两部分内容:①描述了1996年2月3日云南丽江Ms7.0级地震,震前几天的卫星热红外图像呈现圆形,它的NNW、NW、SN、及NE向的热旋扭面往S收敛。该地震地表破裂由一系列张扭性裂缝组成,呈左旋左列,水平位错不明显,垂直断距数厘米。垂直力对构造变动的作用较为明显;而丽江地震震源机制解破裂面II的走向NNE6o,倾向W,倾角44o,P轴方位为NNE3o、仰角75o,近于直立,综合热旋扭面展布、地震地表破裂特征及震源机制解,得出该旋扭椭圆为地幔外侧右旋上涌所造成;②菲律宾萨马岛Ms7.0～7.5强震群及青海共和Ms7.0地震前热应力环椭圆的推进路径。根据这一特征得出交变潮汐力的地球动力学解释。卫星热红外图像震前应力热场的方法是临震预测地震的有效方法,卫星热红外技术辅以震源机制解和地表破裂带力学分析是研究地球动力学有力工具。地球自转速度变化,交变潮汐力和地幔旋扭上涌力是地球动力学的主因。  相似文献   

Recommended Values of ²³⁹Pu, ²⁴⁰Pu and ^239+240Pu Concentrations in Reference Material IAEA-315 (Marine Sediment) Estimated by Thermal Ionisation Mass Spectrometry, Inductively Coupled Plasma-Mass Spectrometry and Alpha Spectrometry     

Taeko Shinonaga  Helmuth Aigner  Dilani Klose  Peter Spinder  Heinz Fröschl  David Donohue 《Geostandards and Geoanalytical Research》2008,32(1):93-101

The recommended concentrations of ²³⁹Pu, ²⁴⁰Pu and ^239+240Pu in reference material IAEA‐315 (marine sediment) were estimated by three analytical methods: isotope dilution thermal ionisation mass spectrometry (TIMS), isotope dilution inductively coupled plasma‐mass spectrometry (ICP‐MS) and alpha spectrometry. The determination of ²³⁹Pu and ²⁴⁰Pu (^239+240Pu by alpha spectrometry) was carried out with samples from randomly selected bottles using each method. Plutonium‐238 was also measured by alpha spectrometry. A plutonium‐242 reference material was used as a spike for the quantitative analysis. The influence of ²⁴²Pu in the samples was therefore calculated; however, this contribution was less than the range of uncertainty and did not influence the final results. The obtained data were statistically analysed using variance component analysis and paired comparison. The combined standard uncertainties from “method/measurement”, “bottle” and “sub‐sample” were in the order of 3 to 6%. The main contributions to the uncertainty were from the material heterogeneity and from systematic differences between methods. Based on this study with twenty‐seven analyses using 10–14 g sample mass, concentrations of (38 ± 3) Bq kg^?1, (28 ± 3) Bq kg^?1 and (66 ± 4) Bq kg^?1 are proposed as recommended values for ²³⁹Pu, ²⁴⁰Pu and ^239+240Pu, respectively, and (9.5 ± 0.4) Bq kg^?1 for ²³⁸Pu as an information value in reference material IAEA‐315. In mass concentration units, these amount to (16.4 ± 1.2) ng kg^?1, (3.3 ± 0.4) ng kg^?1 and (0.015 ± 0.003) ng kg^?1 for ²³⁹Pu, ²⁴⁰Pu and ²³⁸Pu, respectively. The certified reference materials NIST 4350B and NIST 4354 were also analysed by TIMS for quality assurance of the method used in this study.  相似文献   

Springs of Great Britain     

J. B. W. Day 《Environmental Geology》1996,27(2):77-78

Predictably, in a country such as Britain, with its preponderance of consolidated, sedimentary, mainly fissure-flow aquifers, there is a very large number of springs, many of which are, or have been, used for public supply. Migratory springs are a feature of the British (Ur. Cretaceous) Chalk, the most important British aquifer. The Chalk's low specific yield and high capillary moisture retention together give rise to very considerable fluctuations (more than 33 m in some areas) of the unconfined water table. Along the gentle dip slopes of the Chalk (North and South Downs of southern and southeastern England) springs may migrate laterally for several miles, giving rise to seasonal streams locally known as bournes or lavants. However, springs such as at Duncton, West Sussex, at the base of the much steeper scarp slopes of the Chalk, form point sources, the flows from which tend to be relatively steady; such springs commonly supply and are the original reason for the existence of many of the small towns and villages which nestle along the bases of the chalk scarps of Sussex and Kent.Where the Chalk forms coastal cliffs, a number of springs break out at the base of the cliff between high and low tide levels; there are major chalk coastal springs, for instance, at St. Margaret's Bay (Kent) and at Arish Mells, east of Lulworth Cove, Dorset. Such springs are not used for direct supply (their salinity is usually too high) but are indicators of the presence of local reserves of groundwater for possible future development.  相似文献   

鄂尔多斯盆地天环坳陷北段奥陶系烃源岩特征及成熟演化史     

黄志刚  任战利  陈玉林  郑庆荣 《地质学报》2022,96(11):3967-3976

为研究天环坳陷北段下古生界天然气成藏规律，利用探井资料和有机地球化学方法，评价了天环坳陷北段奥陶系烃源岩特征并恢复其成熟演化史。天环坳陷北段奥陶系乌拉力克组和克里摩里组烃源岩有机碳含量和生烃潜量相对较高，烃源岩有机质丰度以中等—好为主，少部分为差烃源岩；三道坎组和桌子山组烃源岩以差为主。干酪根组分鉴定表明，天环坳陷北段奥陶系烃源岩主要为Ⅱ1~Ⅰ型干酪根，热演化程度高，处于生干气阶段。成熟演化史模拟显示，古生代—中生代早期地温梯度低，地层埋藏浅，烃源岩成熟演化程度低。燕山期，由于构造热事件，地温梯度迅速升高，早白垩世烃源岩经历的最高温度超过200℃，达到生气高峰期，早白垩世是油气成藏的主要时期。早白垩世之后，鄂尔多斯盆地整体抬升，地温梯度减小，生烃作用停止。  相似文献   

三工河流域新老绿洲发育度的比较   总被引：1，自引：0，他引：1  

何新梅  李小玉  肖笃宁  李彦 《干旱区地理》2006,29(3):342-347

绿洲是干旱区最重要的景观单元之一。人工绿洲是在干旱条件下经长期人类活动改造而形成的特殊景观。随着人类对绿洲水土资源开发利用程度的不断加强,绿洲呈现出不同的发展阶段。从天然绿洲到人工绿洲,是人类适应和改造干旱区自然环境的历程。在这一人地相互作用的过程中,绿洲显示出明显的发育演化特征。从多学科综合的角度,提出绿洲发育度的概念,并从灌溉体系的建设状况、水资源的利用水平、植被与生态建设、农业发展程度、社会经济水平和绿洲景观结构等7个方面提出了绿洲发育度的评价指标体系,以天山北坡2个人工绿洲为例,从空间上定量比较2个绿洲的发育程度,其中阜康市绿洲发育度高于222团绿洲(阜北农场)。  相似文献   

Increasing of efficiency of desulphurisation processes of coals during thermal destruction     

Turchanina Oksana Satin Vladimir Derevyanko Aleksey 《中国地球化学学报》2006,25(B08):51-52

As is well known, a high content of sulphur in coals is an effect of the post-depositional history of coal seams and one of the most important criteria of its use as a fuel. Sulphur in coals can cause a serious environmental and technological problem during their utilization. This problem is very actual for the Donetsk Basin because 734 mined seams out of the total of 1009 （73%） are comprised of coals with sulphur content -2%. The chemical pre-treatment as a first stage in their processing is widely used in order to effectively obtain the thermal destruction products of coals （such as semi-coke, coke, adsorbents, etc.） and to simultaneously utilize coal wastes. Development in pre-treatment methods for high-sulphur, low-rank coals is especially desirable for reducing the sulphur contents of the solid products. The aim of the present work is to investigate the influence of coal pre-treatment on the yield and composition of thermal destruction products, and the sulphur distribution among different components of the coals of different genetic types by reductivity （low-reduced LRC and reduced RC coals）. The thermal behavior of the coals was studied by means of the Fisher method （heated to 520℃, at a rate of 7℃/min）. The composition of the semi-coking gas was investigated by means of a VTI gas analyzer. The coal samples were chemically treated directly before thermal destruction by the introduction of 1-% solutions of radical polymerization initiator AAD （acrylic acid dinitrile C8H12N4） and products of coal-tar distillation （absorber oil）. Coal pre-treatment increases the semi-coke yield and its coking ability, and changes the liquid/gaseous product ratio.  相似文献   

Controls on low-pressure anatexis   总被引：2，自引：0，他引：2  

C. C. GERBI  S. E. JOHNSON  P. O. KOONS 《Journal of Metamorphic Geology》2006,24(2):107-118

Low-pressure anatexis, whereby rocks melt in place after passing through the andalusite stability field, develops under more restricted conditions than does low-pressure metamorphism. Our thermal modelling and review of published work indicate that the following mechanisms, operating alone, may induce anatexis in typical pelitic rocks without inducing wholesale melting in the lower crust: (i) magmatic advection by pervasive flow; (ii) crustal-scale detachment faulting; and (iii) the presence of a high heat-producing layer. Of these, only magmatic advection by pervasive flow and crustal-scale detachment faulting have been shown quantitatively to provide sufficient heat to cause widespread melting. Combinations of the above mechanisms with pluton-scale magmatic advection, shear heating, removal of the lithospheric mantle, or with each other provide additional means of developing suitable high temperatures at shallow crustal levels to generate low-pressure anatexis.  相似文献